There were a lot of things we didn't expect when watching Avengers: Infinity War; the early death of Loki, Hulk being scared of Thanos, the surprising amount of comedy that was still around, despite the grim story, but the one thing no one thought they would see was Red Skull. The Hydra leader hasn't been seen in an MCU film since Captain America: The First Avenger, which came out way back in 2011.
Fans were pretty disappointed when they found out that Hugo Weaving didn't reprise his role, though the actor did a pretty good imitation of his voice. Because of Weaving's dismissal of the role he did, many of us assumed that he wasn't approached to return but it turns out that wasn't the case.
Slash Film was able to attend the special Infinity War screening hosted by Collider and found out that Weaving was asked if he wanted to return to the film via the Q and A from The Russos. It seems like he had no interest in the character's minimal role, which is why they got someone else to do it.
Considering how the villain has haunted the Marvel Universe, many of us were hoping that the Nazi would have a bigger presence in the MCU but it wasn't meant to be. Weaving did a fine job but the MCU was still stuck in its generic villain phase, so viewers didn't exactly care for the character during 2011's First Avenger.
Avengers 4 comes out on May 3, 2019. It's not yet known if Red Skull will return in that movie.